Some modern communication systems allow a user to communicate with other users even when the user moves to different locations around the world. For example, some communication systems allow the user to receive telephone calls regardless of whether the user is in China or in the United States.
To ensure that users can communicate regardless of their locations, the communication system can store a list that maps information identifying the users to Internet Protocol (IP) addresses of the user's communication devices. For example, the communication system can store a list that maps the usernames of the users to the IP addresses of the users' communication devices. However, if many users use the communication system, such lists can grow very large. Such large lists can decrease performance of the communication system.
Moreover, some countries have privacy regulations that consider data indicating a user's IP address to be private to the user. Accordingly, some countries prevent such data from being stored in jurisdictions that do not have protections on such data. Hence, communication systems that replicate the list at various locations around the world may violate such privacy regulations.